The justices refused Hearn’s appeals about 3 1/2 hours before he was scheduled for execution Wednesday evening for the 1998 murder of Frank Meziere. The stockbroker was carjacked at a Dallas car wash, then shot 10 times by his attacker.

Texas prison officials last week announced they were modifying the three-drug procedure used since 1982. Hearn will be the sixth state prisoner executed this year and the first since Texas switched to single-drug lethal injections.

Hearn’s appeals argued his mental disabilities disqualified him from execution. They also contended he had deficient legal help early in his case and that conflicting court opinions hampered filing of late appeals.